(1) Field of the Invention
This invention relates to projection lithography systems for imaging a pattern on a large substrate, and more particularly relates to an alignable, low-profile substrate chuck for large-area lithography systems featuring a mask and a substrate that is to be imaged in sections while remaining within the depth-of-focus and alignment limits of the projection optics.
(2) Description of Related
Many techniques have been investigated for patterning high-resolution features on large surfaces, most of which involve precision stage devices for movement and positioning of the substrate. Such precision stage devices are expensive, and, while quite precise and effective, sometimes do not have the capacity to maintain position and alignment in all dimensions across the entire substrate.
The projection optics assembly typically needs to be mounted to a heavy, rigid bridge over the stage, and for various reasons typically has a relatively limited clearance above the moving platform of the stage. Techniques of stage-on-stage have been tried, in which a small x-y-theta or x-y-z stage or even an x-y-z-theta stage is mounted on the scanning stage platform for final adjustment. Such stage-on-stage solutions, while inherently possible, tend to be unwieldy and expensive, and tend to take up too much vertical space to fit under the bridge above the stage platform.